Towards understanding the role of K during biomass steam gasification

[摘要] Steam gasification is known to be catalyzed by K. However, the exact mechanisms are not identified to this day. In the present study, the catalytic influence of K on biomass steam gasification and its interaction with Si was investigated. The study was conducted through thermogravimetric analysis (TGA) on rice husks as a Si-rich biomass and K2CO3 as a model K-compound. Experiments were conducted in three different configurations: biomass or inorganic compound alone; mixtures of biomass and inorganic powders; biomass and inorganic compound without contact in a two-compartment crucible. It was shown that K has a catalytic effect on both the pyrolysis and the gasification steps. These effects occur even when the K-compound is not in direct contact with the biomass. Therefore, it demonstrates that the mechanisms involve the gas phase through the volatilization of a K-compound, most likely KOH(g). However, the observed catalytic effect on rice husks was weaker than the effect obtained in the case of beech wood, a Si-poor and more generally ash-poor biomass, under the same conditions. It shows that there is a competition between i) the influence of K on the biomass pyrolysis and char gasification kinetics and ii) the interaction of K with SiO2 inherent to the biomass.

[发布日期] 2020-12-15

[关键词] Steam gasification;Reaction kinetics;Catalysis;Potassium;Silica;Rice husk